Apparatus for counting red blood corpuscles in blood



Oct. 13, 1959 K. E. H. DANIELSSON 2,908,907

APPARATUS FOR COUNTING RED BLOOD CORPUSCLES IN BLOOD Original FiledMarch 27, 1956 Fig.1

United States Patent O fiice APPARATUS FOR COUNTING RED BLOOD CORPUSCLESIN BLOOD Karl Erik Harry Danielsson, Orebro, Sweden Claims priority,application Sweden March 29, 1955 1 Claim. (Cl. 233-26) This applicationis a division of my copending application Serial No. 574,306.

The method hitherto almost exclusively used for the determination of thenumber of red blood corpuscles per unit of volume consists in a verygreat dilution of the blood and counting of the number of bloodcorpuscles in a thin layer of the diluted blood enclosed in a chamberformed between two glasses, a so called Biirker chamber. Said methodinvolves many sources of errors, is therefore inaccurate and is alsocircumstantial and time-con suming.

The present invention has for its object to create a method for thedetermination of the number of red blood corpuscles, which is quickerthan the above-mentioned method and which, above all, gives moreaccurate results and eliminates personal errors to a great extent. Themethod according to the invention consists essentially therein, that atube filled with blood of the investigated sample is centrifuged,whereby the blood corpuscles sedimentate and a border line is formed inthe tube between a lower column enriched with blood corpuscles and anupper blood plasma column practically devoid of blood corpuscles, thatthe centrifugal treatment is cut off after an accurately set time.period equal to a predetermined time period chosen for the apparatusused and being of such a short duration that the downward displacementof the border line is considerably less than the displacement that wouldbe reached as a final result of a very long period of centrifugaltreatment, and that that the downward displacement of the border lineobtained for the sample is compared with displacement values obtained bythe centrifuging, under the same conditions, of a series of differentsamples having a number of red blood corpuscles per unit of volume,accurately determined by known methods, said values preferably beingused for calibrating a scale, on which the number of red bloodcorpuscles per unit of volume of the investigated sample can be directlyread olf. The method is based upon the experience (verified by a greatnumber of comparative determinations) that the border line drop valuesobtained after a short centrifugal treatment are closely related to thenumber of red blood corpsucles, whereas the final value obtained after avery long centrifug'al treatment, i.e. the'hematocrit value, does notgive any true information about the number of red blood corpuscles butmerely about their total volume, wherein the average size of the bloodcorpuscles is a factor.

-The'present invention also relates to a centrifugal apparatusparticularly suited for carrying out the abovementioned method and beingof such a construction as to eliminate personal errors in the handlingthereof, which errors would endanger the accuracy of the newbloodcounting method.

As the centrifugal treatment should be cut ofi after a relatively shorttime, when the border line in the test tube is still dropping rapidly,it is obvious that the accuracy of the new method is dependent thereuponthat the 2,908,907 Patented Oct. 13, 1959 centrifugal conditions arereproduceable with a high de gree of precision. To this end, accordingto the invention, the centrifugal apparatus is provided with means forautomatically maintaining constant the centrifugal Work accomplishedupon the blood samples during each period of operation of thecentrifugal apparatus. Said work is determined by many factors, out ofwhich some are invariable, such as the dimensions and the location ofthe test tube in the centrifugal apparatus, some factors may vary withintolerable limits, such as the frequency and the voltage of the electricnetwork, to which the drive motor of the centrifugal apparatus isconnected, the temperature etc., Whereas the time curve for the speed ofrotation of the centrifugal apparatus during a period of operation is ofa predominant importance for the value of the drop of the border line inthe test tube and for the value of the number of blood corpuscles perunit of volume derived therefrom. Therefore, a main object of theinvention is to provide that the time period of electric connection ofthe drive motor of the centrifugal apparatus is held accurately constantand at a predetermined value.

According to the invention, in order accurately to provide the desiredtime period of operation the centrifugal apparatus is provided with atime switch for disconnecting the motor of the apparatus after apredetermined time of connection. Said time switch may be driven by thedrive motor of the apparatus, so that the switch is released when saidmotor has run a certain number of revolutions. Furthermore, it isimportant that the period of acceleration and the period of decelerationare short in comparison to the period during which the centrifugalapparatus rotates with full speed. In order to get a rapid accelerationa powerful motor should be chosen, and in order to get a rapiddeceleration, according to a feature of the invention, the centrifugalapparatus is pro vided with a braking means, which is engagedautomatically and preferably simultaneously with the motor beingdisconnected.

The invention will be more closely described hereinbelow, referencebeing had to the accompanying drawing, in which Fig. 1 is an elevationalview, partly in cross section, and Fig. 2 is a top plan view, withcertain parts removed, of a preferred embodiment of the centrifugalapparatus forming part of the invention.

In the drawing, the numeral 11 designates a stationary I cover, withinwhich an electric motor 13 with a vertical shaft is arranged. Attachedto the upper protruding end of the motor shaft is a horizontal plate 15,which in its turn carries an exactly centered, conical shell 17. Fourholders 19, in which test tubes 21 may be inserted, are evenly spacedaround and attached to the inside of said shell. In operation of theapparatus, test tubes are inserted in all of the holders, and in thosetest tubes that are not filled with blood, there is inserted a metal pinof the same weight as a filling of blood, whereby the rotary part of thecentrifuge always has the same weight and is fully balanced. The motorshaft is surrounded by a stationary sleeve 22, and another sleeve 23 isaxially displaceable on the sleeve 22, but is held against rotationrelatively thereto. Attached to the sleeve 23 is a horizontal plate 25,the periphery of which carries an annular friction lining 27. Normallysaid lining is pressed against the plate 15 on the rotary top of thecentrifuge by means of a fork 31 which is fulcrumed about pivots 29 andpressed by a helical spring 33- against the lower side of the sleeve 23.Said fork is connected pressed and the fork 31 is swung down,compressing the spring 33, so'that the brake consisting of the members23, 25, 27, is out of action and the top of the centrifuge is free torotate.

Mounted on the cover 11 are an electric connection wire with plug 39 forconnection to an electric network of 220 volts, a main switch 40, acontrol lamp 41 for indicating connection to the network, an adjustmentknob 43 for adjusting the tapping point on a resistance connectedbetween the terminals of the network, and a voltmeter 44 for indicatingthe voltage supplied to the electricmotor 13. Connected in series withthe motor is another switch 45, which is located within the cover 11 andis operable by means of a push rod 46 connected to the fork 31. Thelower end of the motor shaft carries a pinion 47 which by means of atrain of gears is coupled to a gearwheel 49 carrying a cam disk 51. Thegear ratio is 2000zl, and thus the gear wheel 49 and the cam disk Slmake one single complete revolution when the motor shaft makes 2000revolutions. The lever 37 is retained in its shown depressed position bymeans of a hitch 53, and the above-mentioned cam disk 51 is made tocooperate with said hitch in such a manner, that the lever 37 isreleased when the step of the cam disk passes said hitch. v The bloodused for the counting method according to the invention may be bloodtaken by a syringe from a cubital vein and may be diluted with one partof sodium citrate in four parts of blood. A test tube having a length of110 mm. and an inner diameter of 2 mm. is filled with said blood mixtureto a predetermined level, which may be marked by an etched line or maybe the upper edge of the tube. The filled test tube is inserted in aholder 19 in the centrifugal apparatus. The main switch 40 is turned on,the lamp 41 being lighted. By

means of the knob 43 the voltage is adjusted to a certain prescribedvalue, e.g. 200 volts. Then the operator depresses the lever 37. Whenthe lever reaches its lower end position it is caught by the hitch 53,so that the operator immediately can leave hold of the lever. Thiscauses the disengagement of the brake and the simultaneous throwing-inof the switch 45, whereby the motor is connected to the adjusted voltageof 200 volts. The

stance, if it has been found earlier, that a drop of the border line offilm. is obtained when blood having 5 millions of red blood cells percubic millimeter is treated in the apparatus above described and duringthe same time, then it is stated in a tableror ina diagram, that 31 mm.corresponds to 5 millions of blood corpuscles. In the same waycorresponding values of border lined rop and number of blood corpusclesare ascertained for a series of different blood samples, said numberbeing determined as accurately as ever possible by using the bestmethods hitherto known, such as taking the average of a great number ofdeterminations according to Biirker. These pairs of corresponding valuesare then tabulated or shown in a diagram. Said interlation should beworked out beforehand for the aparatus used; it is evident that it isvalid only for certain predetermined conditions of centrifuging, suchas'tirne duration, speed etc. Therefore,

. these conditions must always be truly reproduced when motor nowaccelerates during a period of say 20 seconds,

after which it reaches its full speed. When the motor has run 2000revolutions after its start, which always requires the same total time,say seconds, the curve disk 51 has turned one complete revolution andwhen the step therein passes the hitch 53, the same is let loose. Inthis way the lever 37 is released and is raised by the spring 33,whereby the motor current is cut off and the brake is simultaneouslyengaged, so that the motor stops in approximately 2 seconds. The testtube is now removed, and it proves that the red blood corpuscles havesedimentated, so that there is a rather sharp border line at the middleof the tube, which separates a lower column enriched with red bloodcorpuscles and an upper pale column of blood plasma practically freefrom red blood corpuscles. The period of centrifugal treatment has beenso chosen that said lower column contains not only the blood corpusclesbut also a considerable quantity of blood plasma, for instance as greatvolume of blood plasma as the volume of blood corpuscles, and thereforethe length of said column is practically independent of the average sizeof the blood corpuscles. 'Therefore, had the centrifugal treatment beencontinued, the border line wouldhave dropped further on, and after along time the lower column would have contained practically nothing butblood corpuscles. In this way the hematocrit value could have beenobtained, which also is of interest in certain cases but which does nothave any definite relation to the number of red blood corpuscles.

The length of the upper pale column in the test tube is measured, and bycomparison with the result of earlier tests a figure on the number ofred blood cells per cubic millimeter of the undiluted blood is obtained.For inmaking the blood tests. The values obtained during theabove-mentioned preliminary tests can preferably be used for calibratinga scale for directly reading off the number of red blood cells per unitof volume of the blood contained in a test tube taken out of thecentrifugal apparatus. When a standardized test tube is held againstsaid scale with. its bottom resting against an end support associatedwith the scale, the border line in the test tube points to a figure onthe scale stating the number of millions of red blood corpuscles in acubic millimeter of the blood being investigated. In accordance with theabove-mentioned example, the numeral S will be found on said scale at a.spot situated 31 mm. below the upper end of the scale, which end isflush with the upper edge of the test tube or the filling mark engravedthereon.

An extensive statistical investigation has provedthat theabove-described method affords a high degree of, accuracy and that thewhite blood corpuscles (leukocytes) do not disturb the result, not evenwhen their number is pathologically increased. The method is rapid andcan be performed by untrained personnel, because itdoes not call forspecial care and attention- The course of centrifugal treatment 'iswholly automatic, and the speed and the time period are maintained withan accuracy dependent upon the design of the apparatus and considerablyhigher than if the apparatus were started and stopped manually. I v

The above-described design of the centrifugal apparatus is merely givenas an example, and may be modified in several respects without departingfrom thespirit of the invention. Instead of deriving the motor stoppingand braking impulse from the motor shaft, a time switch driven by aclock movement or similar may be used. It is to be observed that thetime periods and the number of revolutions mentioned above are merelygiven as examples, and that it is possible to standardize the method andthe apparatus on the basis of other numerical values. It is important,however, that the centrifugal apparatuses put upon the market affordpredetermined time periods and/or number of revolutions that are set forgood, so that the operator does not have any possibility of readjustingthe same, thereby endangering the accuracy of the new blood-countingmethod. 7 e

I claim: 7 v

A centrifugal apparatus for use in the determination of the number ofred blood corpuscles per unit of volume of a blood sample, comprising amotor having a vertical shaft, a rotary head attached to the upper endof said motor shaft, a test tube holder mounted in an inclined positionin said head, a switch for electrically connecting and disconnecting themotor, a braking means adapted to cooperate with said head in order tobring it to a rapid stand-still, a manually operable lever, meansconnecting said lever to said switch and to said braking means in orderto connect the motor simultaneously with disengaging the braking means,means for automatically disconnecting the motor and engaging saidbraking means a predetermined time after the operation of said lever, ahitch for locking said lever in an operative position, and a trippingmechanism driven by the motor for releasing said hitch and allowing saidlever to return to its inoperative 5 position.

References Cited in the file of this patent UNITED STATES PATENTS1,398,056 Allison Nov. 22, 1921 10 6 Garver Feb. 19, 1935 Levy May 28,1940 Tholl Apr. 1, 1952 Worley Dec. 6, 1955 Schefiler Dec. 27, 1955Dovas Apr. 17, 1956

